WO2014169442A1

WO2014169442A1 - Downstream type tunnel kiln for coal-based direct reduced iron and production process therefor

Info

Publication number: WO2014169442A1
Application number: PCT/CN2013/074282
Authority: WO
Inventors: 江祥民; 高峰; 王运
Original assignee: 福建省毅成投资发展有限公司
Priority date: 2013-04-17
Filing date: 2013-04-17
Publication date: 2014-10-23

Abstract

The present invention relates to a production process for coal-based direct reduced iron, in particular to a downstream type tunnel kiln for coal-based direct reduced iron and a production process therefor. Disclosed is a downstream type tunnel kiln for coal-based direct reduced iron. The tunnel kiln is a long rectilinear tunnel. Fixed walls and vaults are arranged on both sides and the top of the tunnel. A kiln car runs on a track paved on the bottom of the tunnel. The kiln car loaded with materials enters from a kiln head, moves to a kiln tail and comes out. The main point of composition is: high-temperature flue gas inlets of a combustion device are arranged on both front sides of the tunnel kiln to form a fixed high-temperature heating zone; an exhaust port is located in a location between the middle and the kiln tail. The flow direction of airflow of an induced-draft fan is the same as the mobile direction of the kiln car. The downstream type tunnel kiln for coal-based direct reduced iron and the production process therefor in the present invention can give full play to the function of a reducer, reduce the reduction time and increase the reduction efficiency.

Description

Downflow coal-based direct reduced iron tunnel kiln and production process thereof

Technical field

The invention relates to a coal-based direct reduced iron production process, in particular to a downstream coal-based direct reduced iron tunnel kiln and a production process thereof.

Background technique

The direct reduced iron production process includes a coal-based reduction process and a gas-based reduction process, and a coal-based reduction process includes a shaft furnace method, a rotary kiln method, and a tunnel kiln method. The tunnel kiln method is currently widely used. A tunnel kiln coal-based direct reduced iron production process in the prior art 1 As shown, it includes a tunnel kiln, which is a long linear tunnel with fixed walls and vaults on both sides and top, and a kiln car running on the bottom rail. The combustion equipment is located on both sides of the central part of the tunnel kiln, which constitutes a fixed high-temperature belt-sintering belt. The high-temperature flue gas generated by the combustion flows backwards along the tunnel kiln in the direction of the kiln head under the action of the front end of the tunnel kiln. At the same time, the products entering the kiln are gradually preheated, so that the front part of the kiln constitutes the pre-tropical zone of the tunnel kiln. The cold air is blown into the kiln of the tunnel kiln, and the product of the rear part of the kiln is cooled. After the cold air that has been blown in is heated by the product, it is taken out and sent to the dryer as a heat source for drying the green body. This section constitutes a tunnel. Cooling zone of the kiln.

When the tunnel kiln is working, the kiln car is loaded with the material to be burned, and the vehicle enters from one end of the tunnel kiln (kiln head). After the material is fired in the kiln, the kiln is connected from the other end of the tunnel kiln (kiln tail). The car is output, and then the fired product is removed. The unloaded kiln car is returned to the kiln head to continue loading new materials and then calcined in the kiln.

The production of reduced iron by tunnel kiln method is usually carried out by mixing iron ore powder with reducing agent (pulverized coal) and auxiliary agent (lime, etc.) in a certain proportion, and then filling it into a refractory tank, and sealing the tank after the tank is closed. The code is pushed into the tunnel kiln one by one at a specified time interval on the kiln car. The material on the kiln car is preheated, reduced (sintered) and cooled in the kiln with the operation of the kiln car. During the whole process of the kiln, the material is always enclosed in the tank, and the chemical reaction process in the tank is not In the kiln exposed to the outside of the tank, the gas in the kiln outside the tank is not involved in the chemical reaction process in the tank. After the kiln is discharged, the reduced calcined material is subjected to a process such as separation of slag and iron to obtain qualified direct reduced iron.

The prior art tunnel kiln produces direct reduced iron, which has the following disadvantages: the tunnel kiln belongs to the thermal equipment of countercurrent operation, that is, the material on the kiln car continuously moves in the direction of the reverse flow in the kiln, because the high temperature flue gas is in the kiln. The flow direction is opposite to that of the kiln car (ie, countercurrent flow), causing the reducing gas (H ₂ , CO) generated by the reducing agent (pulverized coal) to flow to the low temperature pre-tropic zone at a higher temperature, and the reducing agent cannot be fully utilized. The effect is that the reducing agent (pulverized coal) is wasted and the reduction time is prolonged. This problem is more pronounced when using a higher volatile coal as a reducing agent. Since the gas in the kiln outside the tank does not participate in the chemical reaction process in the tank, the reduction efficiency is also restricted.

Invention composition

The object of the present invention is to overcome the deficiencies in the prior art, and to provide a downstream coal-based direct reduced iron tunnel kiln capable of fully utilizing the action of a reducing agent, reducing the reduction time, and improving the reduction efficiency, and a production process thereof.

The object of the present invention is achieved by the following route.

A downstream coal-based direct reduction iron tunnel kiln, which is a long linear tunnel with fixed walls and vaults on both sides and at the top. The kiln car is running on the bottom of the track, and the kiln car loaded with materials is used. Since the kiln head enters the kiln tail and moves out, the main point of the composition is that the high-temperature flue gas inlet of the combustion equipment is arranged on both sides of the front part of the tunnel kiln, which constitutes a fixed high-temperature heating belt, and the exhaust port is located in the middle and the kiln. At the position between the tails, the flow direction of the exhauster airflow is the same as the direction of movement of the kiln car.

The downstream coal-based direct reduction iron tunnel kiln production process, the main point is that the following steps are included:

1. Providing a tunnel kiln, which is a long linear tunnel with fixed walls and vaults on both sides and top, and a kiln car running on the bottom of the track, a high temperature flue gas inlet of the combustion equipment It is located on the front sides of the tunnel kiln and forms a fixed high-temperature heating belt. The exhaust port is located between the middle and the kiln.

2, The iron ore powder mixed with the reducing agent and the auxiliary agent in a certain proportion or scattered into the high temperature resistant non-metallic can body, and then placed on the kiln car, or processed into a block of a certain geometric shape, stacked or coded on the kiln car.

3. The kiln car loaded with materials moves from the kiln head to the kiln tail and outputs. The high-temperature flue gas enters the kiln and runs in the same direction as the kiln car. The materials carried by the kiln car are preheated and pulverized coal in the front section of the tunnel kiln. The gas reaction products CO, H ₂ , H ₂ O, etc., together with N ₂ , CO _{2 ,} etc. in the high-temperature flue gas flow to the middle and middle sections of the tunnel kiln, together with the gaseous products of the reduction reaction Discharge, the middle section and the middle section of the tunnel kiln constitute a reduction burning zone, and the high-temperature reducing gas is fully contacted with the high-temperature iron ore powder carried by the kiln car and exposed to the atmosphere in the kiln, and finally the iron ore is transformed. Reducing iron for metals.

The above reducing agent generally refers to pulverized coal.

The high-temperature flue gas discharged from the air inlet flows into the kiln from the front of the kiln, and as the kiln temperature rises, the formation of a micro-positive pressure in front of the kiln in front of the kiln of the high-temperature heating belt can also direct the flow of gas in the kiln, prompting Flowing from the front of the kiln to the back of the ki

Thus, the present invention is a direct reduction metal production process of a tunnel kiln in which the high-temperature reducing gas and the kiln car are in the same direction, and the reducing gas generated in the reduction reaction stage is always distributed in the entire section of the tunnel kiln accompanied by the open material. . In the high temperature flue gas heating process in the front section of the tunnel kiln, the material temperature rise and the reductant (pulverized coal) dry distillation and gasification reaction mainly occur. The pulverized coal retorting process mainly undergoes the following changes: when the temperature of pulverized coal is higher than At 100 °C, the water in the coal evaporates; when the temperature rises above 200 °C, the crystallization water in the coal is released; when it is above 350 °C, the cohesive coal begins to soften and further forms a viscous colloid; To 400 ~ 500 °C most of the gas and tar are precipitated, called a thermal decomposition product; at 450 ~ 550 °C, thermal decomposition continues, the residue gradually thickens and solidifies to form a semi-coke; higher than 550 °C, the semi-coke continues to decompose, and the remaining volatiles (the main component is hydrogen) are precipitated, and the semi-coke weight loss simultaneously shrinks to form a crack; the temperature is higher than 800 At °C, the semi-coke volume shrinks and hardens to form porous coke. When the dry distillation is carried out in the chamber type retorting furnace, the primary thermal decomposition product is in contact with the red hot coke and the high temperature furnace wall, and secondary thermal decomposition occurs to form a secondary thermal decomposition product (coke oven gas).

The object of the present invention can also be achieved by the following means.

An exhaust gas inlet is arranged in front of the tunnel kiln before the high temperature flue gas inlet, and the exhaust port communicates with the waste air inlet through the exhaust gas utilization passage.

In this way, the heat value of the exhaust gas and the useful gas products in the exhaust gas are fully utilized through this passage. The waste heat is used to preheat the material entering the kiln, and the area between the exhaust gas inlet and the high temperature flue gas inlet forms a material preheating zone.

A smoke exhauster is installed in the exhaust gas utilization passage.

The smoke exhauster regulates the flow rate of the exhaust gas and the flue gas in the kiln.

The nozzle of the combustion equipment is arranged in the air inlet of the high-temperature flue gas, and the high-temperature flue gas which is fully combusted by the combustion equipment after the external mixed oxygen is sprayed into the high-temperature heating belt in the front part of the kiln through the nozzle.

The residual oxygen content in the high temperature flue gas will affect the reducing atmosphere in the kiln.

The kiln car loaded with materials enters the kiln in a state of convection with the outside of the kiln, and the kiln reacts directly with the convection outside the kiln.

Oxygen in the air affects the reducing atmosphere in the kiln.

A plurality of temperature sensors are disposed at intervals on the left and right sides of the tunnel kiln and on the upper furnace wall and the bottom wall of the furnace.

A plurality of pressure sensors and gas sampling devices are arranged from the kiln head to the kiln tail.

A pressure sensor and a gas sampling device are placed at a distance of half a meter from the inlet and outlet of the tunnel kiln and at intervals of one meter.

In summary, the present invention has the following advantages over the prior art: (1) Give full play to the gas-based reduction of coal dry distillation and gasification products, and improve the utilization rate of coal-based reducing agents; (2) ) High volatile coal can be utilized, thereby reducing the quality requirements of the coal-based direct reduced iron production process of the tunnel kiln to the reducing agent coal; (3) prolonging the contact time of the reducing gas with the high-temperature iron ore powder and increasing the production capacity ; ( 4 ) reducing the combustion load of the combustion equipment outside the tunnel kiln; (5) after the combustion equipment is installed in the front section of the kiln, it is more conducive to controlling the atmosphere in the reduction tunnel kiln.

DRAWINGS

Figure 1 is a schematic view of the structure of a coal-based direct reduced iron tunnel kiln

2 is an explanatory diagram of a production process of a coal-based direct reduced iron tunnel kiln in the prior art

3 is an explanatory diagram of a production process of a downstream coal-based direct reduced iron tunnel kiln according to the present invention;

The invention will now be described in greater detail with reference to the drawings.

detailed description

Best embodiment:

Referring to Figures 1 and 3, a forward-flow coal-based direct reduction iron tunnel kiln is a long linear tunnel with fixed walls on both sides and at the top. 1 and the vault 2, the track 4 on the bottom runs the kiln car 3, loaded with materials a The kiln car moves from the kiln head to the kiln tail and outputs. The high-temperature flue gas inlet of the combustion equipment is arranged on both sides of the front part of the tunnel kiln to form a fixed high-temperature heating belt, and the exhaust port 5 Located between the middle and the kiln, the flow of the exhaust airflow is the same as the direction of movement of the kiln. An exhaust gas inlet is provided in front of the tunnel kiln before the high temperature flue gas inlet, the exhaust port is connected to the waste air inlet through the exhaust gas utilization passage, and a smoke exhauster is installed in the exhaust gas utilization passage. Nozzle for combustion equipment 6 It is installed in the inlet of the high-temperature flue gas, and the high-temperature flue gas which is fully combusted by the combustion equipment after the external mixed oxygen is sprayed into the high-temperature heating belt in the front part of the kiln through the nozzle. The kiln car loaded with materials enters the kiln in a state of convection with the outside of the kiln, and the kiln reacts directly with the convection outside the kiln. The four-meter length in the middle of the tunnel kiln is arranged on the left and right sides, on the upper furnace wall and on the bottom wall of the furnace. More than 3 temperature sensors. A pressure sensor and a gas sampling device are placed at a distance of half a meter from the inlet and outlet of the tunnel kiln and at intervals of metre from the kiln head to the kiln.

The downstream coal-based direct reduced iron tunnel kiln production process includes the following steps:

1. A forward coal-based direct reduced iron tunnel kiln tunnel kiln as shown in Figures 1 and 3 above is provided.

2, Iron ore powder mixed with a reducing agent (pulverized coal) and additives in a certain proportion or dispersed in a high temperature resistant non-metallic can body, then placed on a kiln car, or processed into blocks of certain geometric shape, stacked or placed in a yard On the kiln car.

3. The kiln car loaded with materials moves from the kiln head to the kiln tail and outputs, and the kiln car loaded with materials enters and exits the kiln in a state of convection with the outside of the kiln, and the convection is isolated from the kiln. The direct reduced iron reaction is carried out under the condition that the high-temperature flue gas enters the kiln and runs in the same direction as the kiln car. The waste heat is used to preheat the material entering the kiln, and between the exhaust gas inlet and the high-temperature flue gas inlet. The material preheating zone is formed in the area, and the materials carried by the kiln car are preheated and pulverized coal retorting and gasification reaction in the front section of the tunnel kiln, and the gaseous products CO, H ₂ , H ₂ O and the N ₂ in the high temperature flue gas are generated. The CO ₂ and the like flow together to the middle and middle sections of the tunnel kiln, and are discharged from the exhaust port together with the gaseous products of the reduction reaction. The middle and the middle section of the tunnel kiln constitute a reduction burning zone, and the high temperature reducing gas and the kiln car The full contact of the high temperature iron ore powder that carries and opens the atmosphere exposed to the kiln eventually converts the iron ore into metal reduced iron.

The parts not described in this embodiment are the same as the prior art.

Claims

A downstream coal-based direct reduction iron tunnel kiln, which is a long linear tunnel with fixed walls (1) and vaults on both sides and top (2) , the kiln car (3) is running on the bottom laying track (4), and the material is loaded (a) The kiln car moves from the kiln head to the kiln tail and outputs. The high temperature flue gas inlet of the combustion equipment is arranged on both sides of the front part of the tunnel kiln to form a fixed high temperature heating belt and exhaust port (5). ) Located between the middle and the kiln, the flow of the exhaust airflow is the same as the direction of movement of the kiln.
According to claim 1 The downstream coal-based direct reduced iron tunnel kiln is characterized in that an exhaust gas inlet is arranged in front of the tunnel kiln before the high temperature flue gas inlet, and the exhaust port is discarded through the exhaust gas utilization passage. The ports are connected.
According to claim 2 The downstream coal-based direct reduced iron tunnel kiln is characterized in that a smoke exhauster is installed in the exhaust gas utilization passage.
The downstream coal-based direct reduced iron tunnel kiln according to claim 1, wherein the nozzle of the combustion device (6) It is set in the inlet of the high-temperature flue gas, and the high-temperature flue gas which is fully combusted by the combustion equipment and then removes oxygen after being mixed with oxygen is sprayed into the high-temperature heating belt in the front part of the kiln through the nozzle.
According to claim 1 The downstream coal-based direct reduced iron tunnel kiln is characterized in that a plurality of temperature sensors are arranged at intervals on the left and right sides of the middle of the tunnel kiln and on the upper furnace wall and the bottom wall of the furnace.
According to claim 1 The co-flow coal-based direct reduced iron tunnel kiln is characterized in that a plurality of pressure sensors and gas sampling devices are arranged from the kiln head to the kiln tail.
According to claim 6 The co-flow coal-based direct reduced iron tunnel kiln is characterized in that a pressure sensor and a gas sampling device are arranged at a distance of half a meter from the inlet and outlet of the tunnel kiln and at intervals of each meter.
1. A tunnel kiln is provided. The tunnel kiln is a long linear tunnel with fixed walls (1) and vaults (2) on both sides and at the top. (4) The kiln car (3) is running on it. The high-temperature flue gas inlet of the combustion equipment is located on both sides of the front part of the tunnel kiln, which constitutes a fixed high-temperature heating belt and exhaust port (5) Located between the middle and the kiln,

2 Iron ore powder mixed with a certain proportion of reducing agent and auxiliary agent or dispersed into a high temperature resistant non-metallic can body, then placed on a kiln car, or processed into blocks of certain geometric shape, stacked or coded on a kiln car ,

3. The kiln car loaded with material (a) moves from the kiln head to the kiln tail and outputs. After the high temperature flue gas enters the kiln, it runs in the same direction as the kiln car. The material carried by the kiln car is preheated and pulverized in the front part of the tunnel kiln. After the dry distillation and gasification reaction, the produced gaseous products CO, H 2 , H 2 O, etc., flow together with N 2 , CO 2 , etc. in the high-temperature flue gas to the middle and middle sections of the tunnel kiln, together with the gaseous products of the reduction reaction. The exhaust pipe is discharged, and the middle and the middle section of the tunnel kiln constitute a reduction burning zone, and the high-temperature reducing gas is fully contacted with the high-temperature iron ore powder carried by the kiln car, and finally the iron ore is converted into metal reduced iron.
According to claim 8 The downstream coal-based direct reduced iron tunnel kiln production process is characterized in that the kiln car loaded with materials enters the kiln in a state of convection air outside the kiln, and the convection state of the air in the kiln is isolated from the kiln. The direct reduction iron reaction is carried out.
According to claim 8 The downstream coal-based direct reduced iron tunnel kiln production process is characterized in that the high-temperature flue gas discharged from the air inlet flows into the kiln from the front of the kiln, and the distributed high temperature heats up as the kiln temperature increases. The belt is kept in a positive pressure relative to the kiln before the kiln.